NK cells provide surveillance for the immune system. They circulate looking for viruses and cancer cells. In lieu of clinical trials, many ME/CFS doctors opt for natural ingredients to boost NK cell activity. Here are three supplements with well documented evidence of raising NK cell number AND function. 

Melatonin has a long history of use and is recognized as a safe alternative for sleep. But with all of the other effects perhaps we should consider regular supplementation as part of a health-promoting lifestyle.